-SSE (streaming SIMD Extensions) - supported by Intel and AMD CPUs. The original version has been updated several times(SSE2, SSE3, and SSE4).
In all cases, software needs to be specifically developed to take advantage of the microcode.
Multiprocessing and Multi-core
Yet another approach to making a computer system faster is to use two or more physical CPUs, referred to as Symmetric Multiprocessing (SMP). An SMP-awere OS can then make efficient use of the processing resources available to run application processes on whichever CPU is "available" This approach is not dependent on software applications being multithreaded to deliver performance benefits. Traditionally, SMP was provided by physically installing two or more CPUs in a multi-socket motherboard. Obviously,this adds significantly to the cost and so is only implemented on servers and high-end workstations.
However, improvements in CPU manufacturing techniques have led to another solution: dual-core CPUs (or Chip Level Multiprocessing [CMP]). A dual-core CPU is essentially two processors combined on the same die. The market has quickly moved beyond dual-core CPUs to multi-core packages with 3, 4, or 8 processors. For desktop computing however, the performance benefits of multi-core are unlikely to increase dramatically unless backed up by improved software design.
Dual-core is not quite the same as SMP and software has to be specially written or updated to take advantage of the architecture. Windows XP SP2 and Vista/7 provide full support.